Cooling apparatuses using air as refrigerant have been recently developed as alternatives of conventional cooling apparatuses using chlorofluorocarbon as refrigerant.
For example, Japanese Laid Open Patent Publication No. H05-106944 discloses a refrigerating apparatus composed of a compressor, a condenser including a blowing fan, a pressure reducing unit, and an evaporator including a blowing fan, which are sequentially connected. This refrigerating apparatus includes a first switching valve that is provided downstream or upstream of the condenser and that opens and closes a refrigerant channel of the condenser, a first bypass circuit that bypasses this first switching valve and the condenser, a second switching valve that is provided in this first bypass circuit and that opens and closes the first bypass circuit, a second bypass circuit that bypasses the pressure reducing device, and a third switching valve that is provided in this second bypass circuit and that opens and closes the second bypass circuit. The well-known refrigerating apparatus is characterized in that the first switching valve is opened, the second and the third switching valves are closed, and the blowing fan of the condenser and that of the evaporator are activated in a refrigerating operation, and in that the first switching valve is closed, the second and the third switching valves are opened, and at least the blowing fan of the evaporator out of the blowing fan of the condenser and that of the evaporator is deactivated in a defrosting operation.
Additionally, Japanese Laid Open Patent Publication No. H11-132582 discloses an air-refrigerant refrigerating apparatus constituted so that a compressor, an air cooler, an air-to-air heat exchanger, and an expansion unit are arranged in an order of an air flow, that the air in a chamber required to be cooled is taken into the compressor through the air-to-air heat exchanger, and that the air output from the expansion unit is blown off into the chamber. This air-refrigerant refrigerating apparatus is characterized by including a first bypass provided with a valve for returning a part of or all of the air from the expansion unit to the air-to-air heat exchanger while bypassing the chamber, and a hot air bypass provided with a valve for taking in the air at 0° C. or higher from an air passage between the compressor and the expansion unit, and for supplying the air to an air passage on an inlet side of the air-to-air heat exchanger.
Finally, Japanese Laid Open Patent Publication No. H11-132583 discloses an air-cooling facility for taking the air within a chamber required to be cooled into an air-refrigerant refrigerator as a refrigerant, and for blowing off a low temperature air from the air-refrigerant refrigerator into the chamber. This air cooling facility includes a frosting unit arranged in an air passage for supplying the low temperature air from the air-refrigerant refrigerator to the chamber required to be cooled, and means for discharging a mixture of floating particles and ice pieces in the air captured by this frosting unit in a solid state or after fusing temporarily to the outside of the frosting unit.
Differently from cooling apparatuses using chlorofluorocarbon as refrigerant, commonly used air-refrigerant cooling apparatuses are designed to directly introduce air used as refrigerant into cooled chambers, to recover the air from the chambers, and to circulate the air. The air within the chamber is mixed with the external air due to going in and out of loads and persons. This causes the refrigerant air to incorporate moisture of the external air. The moisture within the refrigerant air enhances generation of frost. Accordingly, defrosting is an important issue for air-refrigerant cooling apparatuses.